Researchers at McGill University in Montreal have developed the MindHabits Trainer game, in which one exercise shows a grid of faces, with 15 of them frowning and one smiling. The player must find the smiling face as quickly as possible.

In a new study, players reported feeling less stressed, had higher self esteem, and were more confident. The level of the players’ stress hormone, cortisol, fell by 17 percent.

The idea is that through repetitive playing, the mind is trained to focus on the positive aspects of life, according to McGill’s Mark Baldwin.